Hi Don, I have both the prewar and postwar version of these cars. Like you, I have a 763E with the original passenger car consists behind it. A couple of things to look out for are a lot of these have the steps broken off the vestibules. Many years ago I found that original vestibule replacements were available at Madison Hardware but I have no idea if they are available today and if so, where.
The cars are molded out of Bakelite and many have flaking of the maroon paint. There must’ve been a problem back in the 30s and 40s with paint adhesion to Bakelite. Mine have have a slight amount of flaking but many I have seen have significant flaking. I’ve seen some that have been professionally repainted and they look good.
As to what they might cost today I have no idea. I’m sure you can search several sites and find out some of the prices they have sold for in recent months.
Hope this information helps, Jim